1. Field of the Invention
This invention generally relates to a lockup device for a torque converter. More specifically, the present invention relates to a lockup device having an elastic coupling mechanism.
2. Background Information
Torque converters usually include a fluid coupling mechanism for transmitting torque between the crankshaft of an engine and the input shaft of an automatic transmission. A torque converter has three types of bladed wheels (impeller, turbine, stator) located inside for transmitting the torque by means of an internal hydraulic oil or fluid. The impeller is fixedly coupled to the front cover that receives the input torque from the crankshaft of an engine. The hydraulic chamber formed by the impeller shell and the front cover is filled with hydraulic oil. The turbine is disposed opposite the front cover in the hydraulic chamber. When the front cover and the impeller rotate together, the hydraulic oil flows from the impeller to the turbine, and the turbine rotates. As a result, the torque is transmitted from the turbine to the main drive shaft of the transmission.
Generally, a torque converter can perform smooth acceleration and deceleration because it transmits a power via fluid. However, an energy loss occurs due to slip of the fluid, resulting in low fuel consumption. Accordingly, in recent years to improve fuel efficiency, some of the conventional torque converters have included a lockup device for mechanically coupling a front cover on an input side and a turbine on an output side. Specifically, the lockup device is disposed in a space located axially between the front cover and the turbine. When the torque converter reaches predetermined operating conditions, the lockup device of the torque converter causes power from the crankshaft of the engine to be directly transmitted to the automatic transmission, and thus, bypassing the fluid coupling device.
Usually, such lockup devices typically include a damper mechanism or an elastic coupling mechanism having a retaining plate, torsion springs and a driven member. In general, a damper mechanism or elastic coupling mechanism transmits torque from the input rotating member to the output rotating member while absorbing and dampening torsional vibrations imparted to the output rotating member from the input rotating member.
Normally the lockup device has a disc-shaped piston, a retaining plate, at least one torsion spring, and a driven plate or member. The piston can be pressed against the front cover. The retaining plate is secured to an outer peripheral section of the piston. The torsion springs are supported by the retaining plate in a rotational direction and at the outer peripheral side of the retaining plate. The driven member supports the opposing ends of each torsion spring in a rotational direction. The driven member is fixedly coupled to a turbine shell or a turbine hub of the turbine.
When the lockup device is engaged, the torque is transmitted from the front cover to the piston and imparted to the turbine via the torsion springs. Furthermore, as the torque fluctuations are transmitted from an engine to the lockup device, the torsion springs are compressed between the retaining plate and the driven member in the damper mechanism, such that torsional vibrations are absorbed and dampened. In other words, the damper mechanism functions as a torsional vibration dampening mechanism to dampen vibration in the lockup device.
The piston is disposed to divide the space between the front cover and the turbine into a first hydraulic chamber on the front cover side and a second hydraulic chamber on the turbine side. As a result, the piston can move axially close to and away from the front cover due to the pressure difference between the first hydraulic chamber and the second hydraulic chamber. When the hydraulic oil in the first hydraulic chamber is drained and the hydraulic pressure in the second hydraulic chamber increases in pressure, the piston moves toward the front cover side. This movement of the piston causes the piston to strongly press against the front cover.
In the conventional lockup device, the operation of the piston is controlled by the working fluid flowing through the main unit of the torque converter. More specifically, a hydraulic operation mechanism in an external position supplies the working fluid to a space between the piston and the front cover when the lockup device is disengaged. This working fluid flows radially outward through the space between the front cover and the piston, and then flows from its radially outer portion into the main unit of the torque converter. When the lockup device is engaged, the working fluid in the space between the front cover and the piston is drained from its radially inner portion so that the piston moves toward the front cover. Thereby, the friction member arranged on the piston is pressed against the friction surface of the front cover. In this manner, the torque of the front cover is transmitted to the turbine via the lockup device.
Preferably, the lockup device uses a plurality of torsion spring sets that act in series in the rotational direction in order to achieve low rigidity and a wide torsional angle. Each spring set constitutes, for example, a pair of coil springs. An intermediate float body (floating element) is disposed between the pair of coil springs in the rotational direction and connects the pair of coil springs together. The intermediate float body constitutes, for example, a ring-shaped part and a claw that extends from the ring-shaped part to the space between the pair of coil springs. With the lockup device just described, the number of spring sets is limited because the spring sets are arranged on the same circle. Therefore, the twisting torque cannot be increased beyond a certain level.
The piston carries an annular friction member adhered to a position opposed to a flat friction surface of the front cover. This portion of the piston and the friction surface of the front cover form a clutch coupling portion of the lockup device. When a clutch coupling portion of the lockup device operates, the torque is transmitted from the front cover to the piston. Thus, the torque transmitted is further transmitted from the retaining plate to the driven plate via the coil springs, and then to the turbine. Torsional vibrations transmitted from the front cover are absorbed and dampened by the coil springs that are compressed between the retaining plate and the driven plate.
In the lockup device described above, the piston is provided at its outer periphery with an outer cylindrical portion so that the cylindrical portion can bear the load applied by the torsion springs, which are forced radially outward by a centrifugal force. However, this structure suffers from such problems that the outer cylindrical portion increases the weight of the piston, and an annular frictional coupling portion has an excessively high rigidity.
In view of the above, there exists a need for a lockup device for a torque converter which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the invention is to provide a lockup device of a torque converter having a disk-like piston, from which a conventional outer cylindrical portion can be eliminated.
Another object of the present invention is to provide an elastic coupling mechanism for a torque converter lockup device or the like having a sufficient number of sets of elastic members that are arranged so as to act as if the elastic members were arranged end to end in the rotating direction.
According to an aspect of the present invention, a lockup device of a torque converter is provided for transmitting a torque and operating to absorb and dampen torsional vibrations. The lockup device includes a disk-like piston, an output rotary member, an elastic member, a support member and a restricting portion. The disk-like piston is a member for performing a clutch operation. The elastic member is a member for elastically coupling the piston and the output rotary member in a rotating direction. The support member has an outer support portion arranged radially outside the elastic member. The support member is arranged relatively rotatably with respect to the piston and the output rotary member. The restricting portion restricts radial movement of the support member. According to this lockup device, the support member, of which radially outward movement is restricted by the restricting portion, supports the radially outer side of the elastic member by its outer support portion. In this manner, the support member restricts the radially outward movement of the elastic member so that an outer cylindrical portion of the disk-like piston can be eliminated.
According to a second aspect of the present invention, the lockup device of the torque converter of the first aspect of the present invention further has such a feature that the support member further has an inner support portion arranged on the radially inner side of the elastic member. The restricting portion is in contact with the inner support portion, and radially supports the support member.
According to a third aspect of the present invention, the lockup device of the torque converter has such a feature that the restricting portion has an outer peripheral surface in contact with the inner peripheral surface of the inner support portion.
According to a fourth aspect of the present invention, the lockup device of the torque converter of the first aspect of the present invention further has such a feature that the support member further has an axial support portion extending radially inward from the outer support portion for supporting one of axially opposite sides of the elastic member. The restricting portion is in contact with the axial support portion for radially supporting the support member.
According to a fifth aspect of the present invention, the lockup device of the torque converter of any one of the first to fourth aspects of the present invention further has such a feature that the elastic member is formed of a pair of members arranged for compression together in the rotating direction. The support member further has a torque transmitting portion arranged in a space defined in the rotating direction between the paired elastic members. In this lockup device, the support member functions as an intermediate float member with respect to the paired elastic members, and a simple structure can be employed for eliminating an outer cylindrical portion from the piston.
According to a sixth aspect of the present invention, the elastic coupling mechanism is provided with a first elastic member, a second elastic member, a first rotating member, a second rotating member, and an intermediate member. The second elastic member is disposed further inward in the radial direction than the first elastic member. The first rotating member has a first abutting part that abuts against both rotationally facing ends of the first elastic member. The second rotating member has a second abutting part that abuts against both rotationally facing ends of the second elastic member. The intermediate member connects the first and second elastic members such that they act as if they were arranged end to end in the rotating direction. With this mechanism, the first elastic member and second elastic member, which compress together in the rotational direction, are aligned not in the rotational direction but in the radial direction. Therefore, a high twisting torque can be established by increasing the number of spring sets or the like.
According to a seventh aspect of the present invention, the intermediate member of the elastic coupling mechanism of the sixth aspect of the present invention includes: a third abutting part that abuts against both rotationally facing ends of the first elastic member; a fourth abutting part that abuts against both rotationally facing ends of the second elastic member; and a connecting part that connects the third abutting part and the fourth abutting part.
According to a eighth aspect of the present invention, the intermediate member of the elastic coupling mechanism of the seventh aspect of the present invention is provided with an intermediate support part that extends in the radial direction between the first elastic member and the second elastic member.
According to a ninth aspect of the present invention, the connecting part of the elastic coupling mechanism of the eighth aspect of the present invention is provided with a first support part that supports the radially facing outside portion of the first elastic member and a second support part that supports the radially facing inside portion of the second elastic member.
According to a tenth aspect of the present invention, the intermediate member of the elastic coupling mechanism of the sixth aspect of the present invention is provided with a first window part that houses the first elastic member and a second window part that houses the second elastic member.
According to a eleventh aspect of the present invention, the elastic coupling mechanism of the tenth aspect of the present invention includes: a plurality of first elastic members, a plurality of second elastic members, a first rotating member, a second rotating member, and an intermediate member. The first elastic members are aligned in the circumferential direction. The second elastic members are aligned in the circumferential direction and disposed further inward in the radial direction than the first elastic members. The first rotating member has first abutting parts that abut against both rotationally facing ends of the first elastic members. The second rotating member has second abutting parts that abut against both rotationally facing ends of the second elastic members. The intermediate member is a disc-shaped member, is formed with a plurality of window parts that house the first and second elastic members, and connects the first and second elastic members such that they act as if the first and second elastic members were arranged end to end in the rotating direction.
With this mechanism, the first elastic member and second elastic member, which act as if the first and second elastic members were arranged end to end in the rotating direction in the rotational direction, are aligned not in the rotational direction but in the radial direction. Therefore, a high twisting torque can be established by increasing the number of spring sets or the like. More particularly, the structure of this mechanism is simple because the intermediate member is a disc-shaped member in which several windows have been formed.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.